1. Field of the Invention
The present invention relates generally to a video display system and, more particularly, is directed to a stereoscopic video display system in which a television picture which is to be displayed on a cathode ray tube (CRT) or a monitor display can be viewed stereoscopically.
2. Description of the Prior Art
In order to view a television picture displayed on a cathode ray tube (monitor display) stereoscopically, the following system is known. Two video or television cameras located with a spacing nearly equal to the spacing between the human eyes are utilized to generate picture information for a left eye (left signal) and picture information for a right eye (right signal), respectively. The two television cameras are driven in synchronism to provide horizontal and vertical deflections. The left signal is displayed on the monitor as the odd field (hereinafter simply referred to as an O field) and the right signal is displayed as the even field (hereinafter simply referred to as an E field). For viewing, a viewer puts on glasses with a shutter mechanism and the shutters for each eye in the glasses are opened and/or shut off alternately at the above mentioned field period (1/30 seconds in the standard television system) by the shutter mechanism.
According to the prior art stereoscopic video display system, the left and right pictures are alternately reproduced on the picture screen of a monitor display at every 30 Hz repetitively so that flicker becomes conspicuous on the picture screen.
In order to remove such defect, the following system has been proposed. As shown in FIG. 1, the left signal L and the right signal R obtained from two different television cameras are multiplexed in the time axis, or doubled in the line frequency and the left signal L and the right signal R are displayed on the monitor display during one vertical driving period of the television camera, that is during one field period (as shown by V in FIG. 1). References I, II, III, IV, . . . in FIG. 1 designate, respectively, a first field, a second field, a third field, a fourth field, . . . which are displayed on the monitor display at every 1/2 V period.
This previously proposed stereoscopic video display system, however, has defects which will be explained below.
FIGS. 2A to 2H illustrate conditions of the scanning lines provided by this prior art stereoscopic video display system, respectively. FIG. 2A shows the scanning lines obtained from a television camera of a left signal (L) system and FIG. 2B shows the scanning lines obtained from a television camera of a right signal (R) system. The television cameras carry out the scanning in the interlaced scanning manner in synchronism with each other. These scanning lines are respectively marked sequentially with references L1, L2, L3, . . . and R1, R2, R3, . . . Throughout FIGS. 2A to 2H, a solid line represents the O (odd field) and a broken line represents the E (even) field.
The left signal L and the right signal R are both supplied to a line-frequency doubler M and thereby horizontal and vertical periods of these left signal L and right signal R become 1/2 the horizontal and vertical deflection driving periods H and V of the television cameras, that is, the left signal L and the right signal R are both doubled in frequency and are then displayed on the monitor display. FIGS. 2C to 2F illustrate the conditions in which each of the display periods in FIGS. 2C to 2F is 1/2 the display period of FIGS. 2A to 2B.
The left signal L in the O field as shown in FIG. 2A is displayed on the monitor display during the period of the first field I (1/2 V) (O field period on the monitor display) as shown in FIG. 2C. The right signal R in the O field as shown in FIG. 2B is displayed on the monitor display during the period of the second field II (1/2 V) (E field period on the monitor display) as shown in FIG. 2D. Further, the left signal L in the E field as shown in FIG. 2A is displayed on the monitor display during the period of the third field III (O field period on the monitor display) as shown in FIG. 2E. Then, the right signal R in the E field as shown in FIG. 2B is displayed on the monitor display during the period of the fourth field IV (E field on the monitor display) as shown in FIG. 2F. As a result, with respect to the left signal L, the picture on the scanning line L1 and the picture on the scanning line L2 as shown in FIG. 2A and also those on the scanning lines L3 and L4 overlap as shown in FIG. 2G. Also, in the right signal R, similar results occur as shown in FIG. 2H and thus the quality and resolution of the picture is substantially deteriorated.
In this case, it is easy to double the left signal L and the right signal R in frequency by sequentially writing the left signal L and the right signal R in field memories of the left signal (L) system and the right signal (R) system and by reading the signals out therefrom at a speed which is twice the writing speed.